The use of gas under pressure for ejecting pieces from molds has become more and more popular in view of the problems encountered with mechanical ejection systems. In particular, mechanical ejection systems produce unwanted pressure on the pieces during ejection and can therefore damage these pieces. The full description of these problems is found in my earlier issued U.S. Pat. No. 4,653,997 dated Mar. 31, 1987 and its corresponding Canadian counterpart.
In the above referenced patents, I used gas pressure to lift the pin to an operating position. In order to minimize the loss of pressure, I provide an O-ring around the enlarged base of the pin which seats on and rides against the pin recess wall so that the gas cannot escape upwardly other than through the gas passage in the pin. This tight fitting at the base of the pin then requires a high gas pressure to lift the pin. As soon as the pin has been lifted, the high gas pressure is maintained producing a high pressure jet directed at the male molding surface which may, for example, with smaller formed pieces result in an extremely abrupt release of those pieces from the male molding surface.